In known air filter frames for a pack of pleated filter medium, the filter pack is sealingly held in the frame with the aid of glue. The glue extends along the four lateral sides of the filter package over the whole width of these sides in order to ensure that all air entering the filter will pass through the filter medium and not leak out at the sides thereof. The glue is applied in and is filling up an inwardly open channel in frame and functions also to increase the rigidity of the frame. Such frames consist of four elongate profile elements and in the corners of the frame are angle-irons disposed, which have tongues punched out in the material of the angle-irons. These tongues are pressed into the material of the profile elements in order to hold these together and are covered by glue after the mounting of a filter pack in the frame. The angle-irons can be fastened by a machine but the manipulation of such a machine is not easy so in many cases the tongues are instead manually applied.
The objective of the present invention is to improve frames according to the introductory paragraph so that the mounting of a filter pack therein is simplified and less glue is needed in order to ensure that all air entering the filter pack will pass therethrough. A second objective is to design the frame so that the angle pieces can more easily be locked to the profile elements by a machine.